diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py
index f28e0de192..e17d468208 100644
--- a/synapse/appservice/scheduler.py
+++ b/synapse/appservice/scheduler.py
@@ -119,7 +119,7 @@ class _ServiceQueuer:
             return
 
         run_as_background_process(
-            "as-sender-%s" % (service.id), self._send_request, service
+            "as-sender-%s" % (service.id,), self._send_request, service
         )
 
     def enqueue_ephemeral(self, service: ApplicationService, events: List[Any]):
@@ -131,7 +131,7 @@ class _ServiceQueuer:
             return
 
         run_as_background_process(
-            "as-sender-%s" % (service.id), self._send_request, service
+            "as-sender-%s" % (service.id,), self._send_request, service
         )
 
     async def _send_request(self, service: ApplicationService):
diff --git a/tests/appservice/test_scheduler.py b/tests/appservice/test_scheduler.py
index c9d76d13eb..8742f5bee8 100644
--- a/tests/appservice/test_scheduler.py
+++ b/tests/appservice/test_scheduler.py
@@ -207,7 +207,9 @@ class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
 
     def test_send_single_event_with_queue(self):
         d = defer.Deferred()
-        self.txn_ctrl.send = Mock(side_effect=lambda x, y: make_deferred_yieldable(d))
+        self.txn_ctrl.send = Mock(
+            side_effect=lambda x, y, z: make_deferred_yieldable(d)
+        )
         service = Mock(id=4)
         event = Mock(event_id="first")
         event2 = Mock(event_id="second")
@@ -239,7 +241,7 @@ class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
 
         send_return_list = [srv_1_defer, srv_2_defer]
 
-        def do_send(x, y):
+        def do_send(x, y, z):
             return make_deferred_yieldable(send_return_list.pop(0))
 
         self.txn_ctrl.send = Mock(side_effect=do_send)